The invention relates to an infinitely variable traction roller transmission in which power is transmitted through traction rollers pivotally supported between toric input and output discs.
In such transmissions, the traction rollers are mounted on support structures which, when pivoted, cause engagement of the traction rollers with the toric discs in circles of varying diameters depending on the desired transmission ratio. The pivotal traction roller support structures are so supported that they can be moved axially for initiating a change in the transmission ratio. For example, two traction rollers may be supported opposite one another by flexible tension sheets as shown in U.S. Pat. No. 4,086,820 which issued May 2, 1978 to Charles E. Kraus.
In U.S. Pat. No. 4,858,484 by Charles E. Kraus in which two traction rollers are arranged between, and in engagement with, opposite toric traction discs for the transmission of motion therebetween, each traction roller is supported by a pivotal support trunnion which has support rollers disposed at opposite ends thereof and supported on partial circular tracks disposed on the housing's inner surface for direct trunnion support. The traction rollers are supported on the pivot trunnions by force transmitting means which, for inexpensive transmissions, include stacks of Belleville springs. The housing tracks may have a center of curvature which is slightly off-set with regard to the pivot axis of the trunnions in order to provide greater compression of the Belleville spring, that is, greater disc engagement forces in one pivotal end position of the pivot trunnions than in their opposite pivotal end positions.
In the arrangement according to U.S. Pat. No. 4,974,466 cross-links are mounted to the axial ends of the trunnions so as to permit pivotal motion thereof only in unison and in an opposite sense, and the cross-links have overlapping center sections with opposing stop surfaces so arranged as to engage one another in the pivotal end positions of the trunnions for limiting their pivotal movement.
Upon engagement with one another the stop surfaces bring the pivoting movement of the trunnions to a sudden stop, which under certain conditions, may cause slippage between the traction rollers and the traction discs.
It is the principal object of the present invention to avoid slippage under the given circumstances.